VIENNA, Aug 22 (Reuters) - The U.N. nuclear watchdog appears
to have made only limited progress so far in getting Iran to
answer questions about its suspected atomic bomb research,
diplomatic sources said on Friday, three days before a deadline
for cooperation.

Under an accord reached by the U.N. agency and Iran in
November in an attempt to revive the long-stalled investigation,
Tehran agreed in May to carry out five specific steps by Aug. 25
to help allay international concerns.

They include providing information about two issues - for
example, alleged explosives experimentation - that are part of
the inquiry by the International Atomic Energy Agency (IAEA)
into what it calls the possible military dimensions of Iran's
nuclear programme, which Tehran says is peaceful.

The diplomatic sources said Iran and the IAEA may have begun
discussing the two topics, but they did not believe Tehran had
provided the requested information or explanations yet.

They said there was still time for Iran to implement the
measures, noting that it had occasionally waited until the last
minute to make concessions in the past.

But slow-paced cooperation would tend to reinforce Western
impressions that Iran is reluctant to give the IAEA the
information and access to sites and people that it says it needs
for its investigation.

There was no immediate comment from the IAEA or Iran.

Iran denies the nuclear programme has any military
objectives, but it has promised since Hassan Rouhani, a
pragmatist, was elected Iranian president in mid-2013 to work
with the IAEA to clarify its concerns.

Western officials say it is central for Iran to address the
suspicions for the chances of a successful outcome of the
parallel talks on a diplomatic settlement between Iran and the
United States, France, Germany, Britain, China and Russia.

With major gaps remaining over what will be permitted in
Iran's uranium-enrichment programme - activity which can have
both civilian and military uses - those negotiations on ending
the decade-old dispute were extended last month until Nov. 24.

"FIRM COMMITMENT"

IAEA Director General Yukiya Amano said after he held talks
in Tehran on Sunday that implementation of the five steps had
begun and that he expected progress to be made over the coming
week, but he did not give details.

Speaking after talks with Rouhani and other senior
officials, he said he had received a "firm commitment" by Iran
to cooperate with the long-running investigation. He also said
he hoped for an agreement soon on future steps by Iran.

Amano's trip to Tehran was an apparent attempt to push for
progress, after diplomatic sources in July said that the IAEA
was concerned about Iran's lack of engagement with the probe.

After years of what the West saw as Iranian stonewalling,
Iran as a first step in May gave the IAEA information it had
requested about Tehran's reasons for developing exploding bridge
wire detonators, which can be used to set off atomic explosive
devices. Iran says they are for civilian use.

The two issues in the inquiry that Iran agreed to address by
late August concern alleged experiments on explosives that could
be used for an atomic device and studies related to calculating
nuclear explosive yields.

They were among 12 specific areas listed in an IAEA report
issued in 2011 with a trove of intelligence indicating a
concerted weapons programme that was halted in 2003, when Iran
came under increased international pressure. The intelligence
also suggested some activities may later have resumed.
(Editing by Larry King)